1. Field of the Invention
The present invention relates to a display device with a plasma addressed display panel where a display cell and a plasma cell are superimposed via a common dielectric sheet, and more particularly, the present invention relates for a configuration for a driving circuit for a plasma addressed display panel. Additionally the invention relates to a structure for suppressing crosstalk which is dependent on the thickness of a dielectric sheet interposed between the display cell and the plasma cell to separate them from each other.
2. Description of Related Art
There has been proposed a plasma addressed display panel where a plasma cell is utilized for addressing a display cell, and a typical one is disclosed in, e.g., Japanese Patent Laid-open No. Hei 1 (1989)-217396. As shown in FIG. 9, this plasma addressed display panel has a stacked structure consisting of a display cell 101, a plasma cell 102 and a common dielectric sheet 103 interposed therebetween. The plasma cell 102 is comprised of a glass substrate 104 and is joined to the dielectric sheet 103 with a predetermined space kept therebetwen. This space is sealed up with an ionizable gas contained therein. On the inner surface of the glass substrate 104, there are formed striped discharge electrodes 105 in the direction of rows. The striped discharge electrodes 105 function alternately as anodes and cathodes to generate plasma discharges 106 therebetween. Each pair of the anodes and cathodes constitute a discharge channel. Meanwhile the discharge cell 101 is comprised of a glass substrate 107. This glass substrate 107 is disposed opposite to the dielectric sheet 103 through a predetermined gap, which is filled with an electro-optical substance such as a liquid crystal 108. Striped signal electrodes 109 are formed on the inner surface of the glass substrate 107. The signal electrodes 109 extend in the direction of columns and intersect orthogonally with the row-direction discharge channels, wherein matrix pixels are located at the intersections of the signal electrodes and the discharge channels. In the plasma addressed display panel having such a structure, display driving is performed by line-sequentially switching and scanning the striped discharge channels where plasma discharges 106 are generated and simultaneously applying, in synchronism with the scanning, picture signals to the signal electrodes 109 on the side of the display cell 101. Upon generation of plasma discharges 106 in the discharge channels, the inside is turned to the anode potential substantially uniformly, and the pixels are selected per row. That is, each discharge channel functions as a sampling switch. When a picture signal is applied to each pixel in an conducting state of the sampling switch, the pixel can be turn on or off under control. And even after the sampling switch is turned to its non-conducting state, the picture signal is still held in the related pixel and thus a sample-and-hold action is performed.
The problems to be solved by the present invention will now be described below with reference to FIG. 9. In the plasma addressed display panel where a picture signal is written by utilizing a plasma discharge, there occurs crosstalk termed "data diffusion" in the direction orthogonal to the signal electrodes 109 (along the discharge channels) resulting from the thickness of the dielectric sheet 103 which separates the liquid crystal 108 and the discharge channel from each other. This crosstalk called, data diffusion, is caused by the interference between the data of adjacent pixels. This phenomenon results in poor color representation, and in a worse case, in degrading the horizontal resolution. For this reason, the color reproducibility is inferior in such a color display. Hereinafter an explanation will be given on a mechanism of causing such data diffusion. As shown in FIG. 9A, a plasma discharge 106 is generated at the time of writing a picture signal in each pixel, and after selection of the pixel, a picture signal supplied to the signal electrode 109 is written in a liquid crystal capacity. Subsequently, as shown in FIG. 9B, the plasma discharge is brought to a halt to induce a non-selected state, whereby the picture signal is held. First, when the picture signal is written, a charge pattern corresponding to the picture signal is formed on one side of the dielectric sheet 103 in contact with the plasma discharge 106. However, since the total thickness of the liquid crystal 108 and the dielectric sheet 103 is so large as to be nonnegligible in comparison with the pixel pitch, the charge pattern thus formed fails to be completely coincident with the shape of the pixel, and consequently the charge pattern is expanded with the data diffusion. During the picture signal holding period (almost the entire period of the actual operation time, e.g., 479/480), as shown in FIG. 9B, an electric field is selectively applied to the inside of the liquid crystal 108 by the charge pattern 110 formed on one side of the dielectric sheet 103 which is in contact with the plasma discharge, so that the liquid crystal 108 is driven. As the voltage level of the picture signal during this period is zero volts on average, the electric lines of force at this time are such as illustrated, so that an electric field, which is further expanded than the charge pattern formed at the time of writing the picture signal, is applied to the liquid crystal 108. Upon the occurrence of such data diffusion, color mixture is caused to induce deterioration of the color reproducibility as a result in case striped color filters are formed for example correspondingly to the striped signal electrodes. Further, there arises another serious problem that the resolution is lowered in a direction orthogonal to the striped signal electrodes.